Safety circuit

Abstract

A safety circuit (12) for the surveillance of the proper functioning of an electronic wheel lockup-protected motor vehicle brake system includes automatic control circuits (10, 38), automatically controlled magnet valves (4, 46), and pick-up transducers (3, 47) at the motor vehicle wheels (2, 48) to be monitored. An error message and/or a partial shut-off of a defective pair of circuits, relating to wheel lockup protection circuits relating to diagonally disposed wheels, occurs in this safety circuit when an upward jump or a downward jump is recognized in the measured velocity of the one wheel and, simultaneously, the speed of the diagonally, oppositely disposed wheel or of any other wheel is measured to be above a limiting value. It is thereby avoided that an undesired error message occurs already when a jump in velocity is recognized, for instance in case of a standing vehicle, in case of a starting of the motor, or in case of a beginning of rolling of the vehicle.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims: 
     
       1. A safety circuit for monitoring of the functioning of an electronic wheel lockup-protected motor vehicle brake system comprising an electronic system furnishing an error signal in a case where a jump in a velocity signal of one wheel is recognized as an erroneous signal and where simultaneously the velocity of the diagonally, oppositely disposed wheel is found to be at a value higher than a predetermined limiting value;   wherein the electronic system comprises   a first wheel;   a first automatic locking control circuit having an input derived from monitoring the speed of the first wheel and having an output;   a first circuit part having an input connected to the output of the first automatic locking control circuit and including a first jump-recognition circuit of a predetermined circuit part for detecting an upward jump in velocity,   a second jump-recognition circuit of the predetermined circuit for detecting a downward jump in velocity,   a first comparison circuit for monitoring the speed of the first wheel, and   an output of the first circuit part;   a second wheel;   a second automatic locking control circuit having an input derived from monitoring the speed of the second wheel and having an output;   a second circuit part having an input connected to the output of the second automatic locking control circuit, wherein the second circuit part includes   said first jump-recognition circuit of a predetermined circuit part for detecting an upward change in velocity,   said second jump-recognition circuit of the predetermined circuit for detecting a downward jump in velocity,   a second comparison circuit for monitoring the speed of the second wheel, and   an output of the second circuit part, and   a logic circuit having a first input connected to the output of the first circuit part and having a second input connected to the output of the second circuit part for providing a joining of the first circuit part and of the second circuit part to form a safety circuit.   
     
     
       2. The safety circuit according to claim 1, wherein the first jump recognition circuit of the first circuit part has an output forming part of the output of the first circuit part;   wherein the second jump recognition circuit of the first circuit part has an output forming part of the output of the first circuit part;   wherein the firs comparison circuit of the first circuit part has an output forming part of the output of the first circuit part;   wherein the first jump recognition circuit of the second circuit part has an output forming part of the output of the first circuit part;   wherein the second jump recognition circuit of the second circuit part has an output forming part of the output of the first circuit part;   wherein the second comparison circuit of the first circuit part has an output forming part of the output of the first circuit part;   wherein the logic circuit comprises four AND gates wherein each AND gate includes two inputs, which two inputs are connected to respective outputs of the jump-recognition circuits and to the respective outputs of the comparison circuit, whereby the outputs of the jump-recognition circuits and the outputs of the comparison circuits are connected to the inputs of an OR gate.   
     
     
       3. The safety circuit according to claim 1, wherein the jump recognition circuits are activated when there occurs an upward jump in velocity from about zero to more than a lower limit speed and when a wheel speed limit is set to a lower limit speed.   
     
     
       4. The safety circuit according to claim 1, wherein the jump recognition circuits are activated when there occurs a downward jump in velocity of more than an upper limit speed down to about zero, and when a wheel speed limit is set to a lower speed limit.   
     
     
       5. The safety circuit according to claim 1, wherein the safety circuit includes a microprocessor.   
     
     
       6. The safety circuit according to claim 1, wherein the safety circuit includes an integrated circuit.   
     
     
       7. The safety circuit according to claim 1, wherein the logic circuit has a signal output and further comprising a storage and amplifier circuit having an input connected to the output of the logic circuit and having an output;   a signal device having an input connected to the output of the storage and amplifier circuit, wherein the storage and amplifier circuit activates the signal device furnished for a respective diagonal system associated with two diagonally disposed wheels.   
     
     
       8. The safety circuit according to claim 7, wherein the signal device is a lamp. 
     
     
       9. The safety circuit according to claim 7, wherein the signal device is a shut-off relay. 
     
     
       10. The safety circuit according to claim 1, further comprising a partial shut-off of electronic circuitry.   
     
     
       11. The safety circuit according to claim 1, wherein the jump recognition circuits are activated when there occurs a downward jump in velocity of more than an upper limit speed down to about zero, and when a wheel speed limit is set to a lower speed limit;   wherein the safety circuit includes a microprocessor.   
     
     
       12. The safety circuit according to claim 1, wherein the safety circuit includes a microprocessor;   wherein the safety circuit includes an integrated circuit;   wherein the logic circuit has a signal output and further comprising   a storage and amplifier circuit having an input connected to the output of the logic circuit and having an output; a signal device having an input connected to the output of the storage and amplifier circuit, wherein the storage and amplifier circuit activates the signal device furnished for a respective diagonal system associated with two diagonally disposed wheels;   wherein the signal device is a lamp.   
     
     
       13. A safety circuit (12) for monitoring of a proper functioning of an electronic wheel lockup-protected motor vehicle brake system, wherein an error signal and a partial shut-off of electronic circuitry occurs in a case where a jump in velocity signal of one wheel is recognized as an erroneous signal and where simultaneously the velocity of the diagonally, oppositely disposed wheel or of another wheel is found to be at a higher value than a predetermined limiting value; where the safety circuit (12) comprises two circuit parts (22, 23), where each part is coordinated to a respective automatic control circuit (10, 38), where the circuit parts (22, 23) of the safety circuit (12) comprise, in each case, a first jump-recognition circuit (15, 25) for detecting an upward jump in velocity, a second jump-recognition circuit (17, 29) for detecting a downward jump in velocity, and a comparison circuit (16, 27) for monitoring of a wheel speed limit, where the two circuit parts (22, 23) are connected to each other via a successively disposed logic circuit (18, 19, 26, 28),   
     
     
       14. The safety circuit according to claim 13, wherein the logic circuit comprises four AND gates (18, 19, 26, 28), which AND gates, in each case, include two inputs, which two inputs are connected to the outputs of the jump-recognition circuits (15, 17, 25, 29) and to the outputs of the comparison circuits (16, 27), wherein the outputs of the jump-recognition circuits (15, 17, 25, 29) and the outputs of the comparison circuits (16, 27) are connected to the inputs of an OR gate (20). 
     
     
       15. The safety circuit according to claim 13, wherein the jump recognition circuits (15, 25, 17, 29) are activated when there occurs an upward jump in velocity from about zero to ±7 km/hour, or when there occurs a downward jump in velocity of more than 11.2 km/hour down to about zero, and when a wheel speed limit is set to 7 km/hour. 
     
     
       16. The safety circuit according to claim 13, wherein the safety circuit (12) includes a microprocessor.   
     
     
       17. The safety circuit according to claim 13, wherein the signal output (30) of the safety circuit (12) is connected to a storage and amplifier circuit (35), which storage and amplifier circuit (35) triggers a signal device such as a lamp (36) and/or a shut-off relay (37, 40) for a respective diagonal formed by two wheels. 
     
     
       18. The safety circuit according to claim 13 wherein the safety circuit includes an integrated circuit.   
     
     
       19. A monitoring method for assuring a proper functioning of an electronic wheel lock-up protected motor vehicle brake system comprising monitoring a jump in a velocity signal of a first wheel;   monitoring the velocity of a second wheel;   recognizing the jump in the velocity signal of the first wheel as an erroneous signal in a safety circuit;   generating an error signal, where a jump in the velocity signal of one wheel is recognized as an erroneous signal and where simultaneously the velocity of the diagonally, oppositely disposed wheel or of another wheel is found to be at a higher value than a predetermined limiting value;   further comprising detecting an upward jump in a first wheel velocity in a first jump-recognition circuit; detecting a downward jump in a first wheel velocity in a second jump-recognition circuit;   monitoring a wheel speed limit in a comparison circuit; comparing the detecting results and the monitoring results with those of another wheel in a logic circuit.   
     
     
       20. The monitoring method according to claim 19 further comprising amplifying a signal output of the logic circuit in an amplifier circuit; triggering a signal device with an output signal of the amplifier circuit for a respective diagonal formed by two wheels. 
     
     
       21. The monitoring method according to claim 19 further comprising activating jump recognition circuits when there occurs an upward jump in velocity from about zero to a lower limit value, or when there occurs a downward jump in velocity of more than an upper limit value down to about zero, and when a wheel speed limit is set to the lower limit value.   
     
     
       22. The monitoring method according to claim 19 further comprising activating jump recognition circuits when there occurs an upward jump in velocity which is sensed by a pick-up transducer disposed near a respective wheel from about zero to a lower limit value, or when there occurs a downward jump in velocity of more than an upper limit value down to about zero, and when a wheel speed limit is set to the lower limit value.   
     
     
       23. The monitoring method according to claim 19 further comprising partially shutting-off electronic circuitry in a case where a jump in velocity signal of one wheel is recognized as an erroneous signal.